Increase the speed of the bevel tool mouse-drag
You can go into user preferences under input and change the settings used.


Searching for bevel will quickly find what you want.
Change the amount type to Percent.
You could also change the amount setting so that it starts at say 5
Save user settings so that it remains the default option when you restart blender.




After using the bevel tool, you can adjust the settings that were used, these settings are available at the bottom of the toolbar region or by pressing F6.

If you look at the header of the 3D Viewport while using the bevel tool (and other tools), you will see a list of available options that can be used while interactively using the tool.

For the bevel tool, press M to change the mode, use the  mouse wheel to change the number of segments. You can also type in the amount you want, so if you have mode set to percent you can type 25 to get a 25% bevel, you can also use backspace before accepting the bevel to adjust the setting you type in.